Handle watching a non-existent directory.

pkg/watcher/test/directory_watcher_test.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import 'package:scheduled_test/scheduled_test.dart';
 
 import 'utils.dart';
 
 main() {
   initConfig();
@@ skipping 68 matching lines @@
     writeFile("a.txt", contents: "after", updateModified: false);
     writeFile("b.txt", contents: "after");
     expectModifyEvent("b.txt");
   });
 
   test('watches files in subdirectories', () {
     createWatcher();
     writeFile("a/b/c/d/file.txt");
     expectAddEvent("a/b/c/d/file.txt");
   });
+
+  test('watches a directory created after the watcher', () {
+    // Watch a subdirectory that doesn't exist yet.
+    createWatcher(dir: "a");
+
+    // This implicity creates it.
+    writeFile("a/b/c/d/file.txt");
+    expectAddEvent("a/b/c/d/file.txt");
+  });
+
+  test('when the watched directory is deleted, removes all files', () {
+    writeFile("dir/a.txt");
+    writeFile("dir/b.txt");
+
+    createWatcher(dir: "dir");
+
+    deleteDir("dir");
+    expectRemoveEvents(["dir/a.txt", "dir/b.txt"]);
+  });
 }